For those of us who don't have Photoshop on our computers and don't want to pay big bucks for it, there is a free one out there that works very well. It will allow you to resize you pictures so that they fit within the message. (Note the screen size data at the top of each message screen - that will give you an idea - resize photos to no more than 600 pixels)(or use inches - no more than 4x6). It's actually a good photo software, works with a ride range of photo formats. I think it was this guy's graduate thesis.
Anyway, I ran across this when was doing a training for my online classes.
http://www.irfanview.com
Pam